ARMY TM 9-2815-253-24 AIR FORCE TO 38G1-93-2 MARINE CORPS TM 2815-24/3 CHAPTER 2 OPERATION SECTION I.  PRINCIPLES OF OPERATION 2-1. INTRODUCTION. This section contains functional descriptions of the engine systems and how they are connected to the end item. 2-2. COOLING SYSTEM. The cooling system consists of a radiator, hoses, thermostat, belt driven fan, water pump, and cooling jackets within the engine.  The water pump forces coolant through passages (coolant jackets) in the engine block and cylinder head where coolant absorbs heat from the engine.  When the coolant temperature is below operating temperature, the thermostat is closed and coolant is bypassed to the water pump inlet.  As coolant temperature increases to 1600F (71 0C), the thermostat starts to open, restricting bypass flow and opening flow to the radiator.  As coolant temperature continues to increase to 1850F (850C), the thermostat is fully opened, shutting off all bypass flow and providing full flow through the radiator.  Air forced through the fins of the radiator by the fan cools the coolant pumped through the radiator.  Items are added to the engine to monitor coolant temperature and to warn if temperature exceeds a predetermined value. 2-3. LUBRICATION SYSTEM. The lubrication system consists of an oil sump, dipstick, pump, relief valve, and filter.  The oil sump is a reservoir for lubricating oil.  The dipstick indicates oil level in sump.  The pump draws oil from the sump through a screen which removes large impurities.  The oil then passes through a relief valve preset to limit oil pressure to 47 to 59 psi (324 to 407 kPa).  The oil then passes through a spin-on type filter where small impurities are removed.  From the filter, oil enters the cylinder head oil gallery and flows to the crankshaft and bearings.  The connecting rod bearings are pressure fed through internal drillings in the crankshaft from the supply to the main bearings.  Splash oil lubricates the gears, and the underside of the pistons.  The governor camshaft is lubricated by a drilled bolt/oil jet.  An internal crankcase drilling provides an oil feed to the hydraulic tappets.  After passing through the block, the oil returns to the oil sump.  Items are added to monitor oil pressure and to warn/stop engine if pressure drops to a dangerously low value. 2-4. FUEL SYSTEM. 2-4.1. The fuel system consists of an external fuel tank, electrically driven transfer pump, fuel filter/water separator, fuel filter, fuel injection pump and fuel injector for each cylinder, and piping.  Fuel from an external source is supplied to the fuel injection pumps.  The injection pumps provide a pressurized metered quantity of clean atomized fuel through the injector nozzles into the cylinders at a precise time near the end of the compression stroke of each piston.  The fuel that is not used by the injectors is returned to the fuel tank via an excess fuel return line. 2-4.2. Extremely cold outside temperatures make starting the engine difficult.  To improve engine starting, a cold weather starting aid has been provided that features four heater plugs in the intake manifold.  The heater plugs are energized during engine preheat starting cycle. 2-5. ELECTRICAL SYSTEM. The electrical system consists of external mounted batteries, starter, battery charging alternator, and related relays and switches for control of the system.  Battery power supplied to the starter during the start cycle energizes the starter which engages the ring gear of the flywheel causing the engine to turn over.  When engine start is complete, the starter is deenergized and disengages from the flywheel. SECTION II.  OPERATING INSTRUCTIONS NOTE Refer to end item operator's manual. 2-1/(2-2 blank)